1. Field of the Invention
The invention relates in general to elevator systems, and more specifically to stopping or landing arrangements for elevator systems.
2. Description of the Prior Art
It is important in elevator systems to consistently stop an elevator car at the various floor levels of the associated structure with very little error, and to do so with an acceptable floor-to-floor time achieved within predetermined limits of acceleration, deceleration, and rates of change of acceleration and deceleration. These requirements are met by elevator systems which utilize a direct current drive motor, an adjustable source of direct current voltage, and feedback control which continuously adjusts the magnitude of the direct current voltage applied to the direct current motor to cause the elevator car to closely follow a reference speed pattern.
The initial cost of an elevator system may be reduced by using an alternating current drive motor, but the overall performance of the elevator system is below that of systems which use direct current drives, and thus the alternating current systems are used only at the low end of the traction elevator speed range. Because of the initial cost advantage of the alternating current elevator drive system, compared with the direct current elevator drive system, it would be desirable to improve the operation of an elevator system having an alternating current drive motor, enabling such system to be extended to higher car operating speeds without sacrificing landing accuracy, floor-to-floor time, and passenger comfort.